Isolation switch for fibre channel fabrics in storage area networks

ABSTRACT

An isolation switch blade Fibre Channel switch presents F_ports to form a first Fibre Channel fabric and N_ports to a second Fibre Channel fabric to appear as node devices. The isolation switch blade may be used to connect a plurality of blade servers to a Fibre Channel fabric. Fabric events engendered by the insertion or removal of hot-pluggable devices are handled by the isolation switch blade and “event storms” on the Fibre Channel fabric are avoided. The isolation switch blade presents the blade servers to the FC fabric as a virtualized N_port.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to storage area networking using the FibreChannel protocol. More particularly, it relates to storage area networksconnected to blade-type file servers.

2. Description of the Related Art

The scaling of dynamic Fibre Channel fabrics is a challenging problem.When switches are added to or removed from a fabric they tend toprecipitate high volumes of control traffic, causing the CPUs of theconstituent switches to get overloaded, and often result in productiondata disruption due to fabric re-configurations. Fabrics also tend tobecome unstable while handling large volumes of fabric events. Theseissues are further exacerbated by the growing trend to blade servers.The host processor blades in the blade servers are intended to behot-pluggable. Further, any Fibre Channel switch located on a bladewould also be intended to be hot-pluggable. This makes fabrics even moredynamic and places increasingly higher scalability requirements on FibreChannel fabrics. The hot-plug capabilities of these, possibly large,numbers of host and switch blades increases the probability of “eventstorms,” resulting in loading or disrupting the enterprise fabrics theyare connected to. These problems may ultimately result in loss ofservice (e.g., host bus adapter logins may timeout) under heavy loadconditions in the fabric. It would be desirable to be able to use hostblades and switch blades in blade servers without having the problemsdiscussed above.

SUMMARY OF THE INVENTION

An isolation switch blade according to the present invention presentsthe facade of a switch to a fabric formed of the host processor bladesand that of a host to the enterprise fabric and performs controlledmediation of data and control traffic between the blade fabric and theenterprise fabric. The multiplexing of multiple streams of trafficbetween the N_ports on the host processor blades and the enterprisefabric is accomplished by a feature in certain Fabric Operating Systems(FOS) called “N_port Virtualization” (NPV). One particular NPV mechanismis described in U.S. patent application Ser. No. 10/356,659 filed Jan.31, 2003 and entitled “Method and Apparatus for Providing Virtual Portswith Attached Virtual Devices in a Storage Area Network” and in U.S.patent application Ser. No. 10/209,743 filed Jul. 31, 2002 and entitled“Method and Apparatus for Virtualizing Storage Devices inside a StorageArea Network Fabric.” Further information is provided in U.S. patentapplication Ser. No. 10/201,331 filed Jul. 23, 2002 and entitled “FibreChannel Virtual Host Bus Adapter.” The disclosures of these three patentapplications are incorporated herein by reference. Using the NPVmechanism, the number of host processor blades that can simultaneouslybe plugged in, and to which virtual N_port identifiers can be assigned,is 255 (using a one-byte port id), which is a sufficiently large numberto accommodate the number of blades in present day blade server chassis.

An isolation switch blade according to the present invention can beconnected to multiple enterprise fabrics, so the N_port identifierswithin the enterprise fabrics may be mapped to proxy addresses that arescoped by the fabric. All control traffic address mappings betweenvirtual and physical addresses may be mediated and translated by the CPUof the isolation switch blade and address mappings for data trafficperformed at wire speed.

The use of N_port virtualization also enables the isolation switch bladeto act as an initiator, which is advantageous as this allowspartitioning of fabrics and isolation of the enterprise fabric fromexchanges originating from the host processor blades. Since the hostprocessor blades are not directly connected to the enterprise fabric,the enterprise fabric is isolated from large amounts of fabric activitydue to host processor blades being swapped in and out. This isolationpromotes scalability within the enterprise fabric. Since the isolationswitch blade may preferably be a single conduit into the enterprisefabric, it is also a good point to enforce perimeter defenses (similarto a firewall) against attacks, either intentional or resulting frommisbehaviors. The isolation switch blade may also act as a throttle bycontrolling the host processor blade access into the enterprise fabric.Further, the isolation switch blade may act as a protocol gateway. Inaddition, the use of the N_port connection increases interoperability,as compared to using an E_port connection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of an isolation switch blade inlogical communication with four host blades and an enterprise fabricaccording to the present invention.

FIG. 2 is a schematic representation of a system in which four hostblades are connected to a pair of isolation switch blades according tothe present invention.

FIG. 3 is a schematic representation of a Fibre Channel enterprisefabric in logical communication with a firewall/intrusion detector in anisolation switch blade according to the present invention.

FIG. 4 is a schematic representation of a dual connected host-targetconfiguration according to the present invention.

FIG. 5 is a schematic representation of an isolation switch blade withpath fail over according to the present invention.

FIG. 6A is a representation of frame flow from a host blade to a targetin the enterprise fabric according to the present invention.

FIGS. 6B and 6C are blocks of exemplary isolation switch bladesaccording to the present invention.

FIG. 6D is an illustration of the software modules in an isolationswitch blade according to the present invention.

FIG. 7 depicts a fabric initialization and login procedure according tothe present invention.

FIG. 8 is an exemplary PID mapping table according to the presentinvention.

FIG. 9 depicts a device registration and discovery procedure accordingto the present invention.

FIG. 10 depicts zoning in an enterprise fabric according to the presentinvention.

FIG. 11 shows load balancing and fail over with two isolation switchblades according to the present invention.

FIG. 12 shows the use of a Fibre Channel authentication protocolaccording to the present invention.

FIG. 13 shows an alternative embodiment with the connection of anisolation switch blade to an enterprise fabric as an E_Port according tothe present invention.

DETAILED DESCRIPTION

Many organizations have begun consolidating their file servers intocentralized data centers, looking to use physical, application or dataconsolidation as a means of reducing the challenges and costs associatedwith administering many small file servers scattered across theenterprise. To date, physical consolidation has generally involvedreplacing bulky tower servers with slender 1U or 2U rack systems. Suchrack systems take less space and put the servers and infrastructurewithin easy reach of the network administrator, rather than spreadacross a large area.

These servers enable organizations to reap many benefits ofconsolidation, yet because each server requires its owninfrastructure—including, e.g., cables for power, Ethernet, systemsmanagement, power distribution units (PDUs), keyboard/video/mouse (KVM)switches and Fibre Channel switches—they present challenges of theirown. A rack of 1U servers can have hundreds of cables strung throughoutthe rack, making it difficult to determine which cables attach where andcomplicating the addition and removal of servers to and from the rack.In addition, the PDUs and switches consume valuable rack sidewall space.A blade server eliminates many of these complications, thus providing aneffective alternative to 1U and 2U servers.

The term “blade server” refers to a rack-optimized server that can holda number of hot-swappable devices called blades. There is a range ofblade server designs—from ultra-dense, low-voltage, lesser-performingservers to high-performance, lower density servers to proprietary,customized rack solutions that include some blade features.

An isolation switch blade (ISB) according to the present invention maybe a Fibre Channel (FC) switch in the blade form factor that is housedin a chassis that may include Ethernet switch modules, Fibre Channelswitch modules, KVM management modules, power supply modules, a midplaneand host blades (all not shown). An example of such a device is the IBMeServer BladeCenter. In addition to providing FC switching capabilities,the isolation switch blade may also incorporate advanced capabilitiesfor providing failure and security isolation, and can facilitateenterprise fabric scaling. Another benefit of the isolation switch bladeis that it can be interoperable with a variety of switches since it canconnect to the fabric as an N_port rather than as an E_port in thepreferred embodiment.

This disclosure describes the architecture of an isolation switch bladeaccording to the present invention. The role of an isolation switchblade is to enable Fibre Channel fabrics to behave well when bladeservers are connected to them. Fibre Channel fabrics comprise one ormore Fibre Channel switches connected in some networked topology.

Blade servers introduce a level of service distribution (distribution ofapplications across blades to scale out) that is not as common incurrent ‘monolithic’ servers, which are typically configured to run anenterprise application running on a single server. Furthermore,misbehaving host bus adapters (HBAs) might induce control traffic, e.g.repeatedly doing FLOGIs (fabric logins, a process by which a node makesa logical connection to a fabric switch) and, with the introduction of alarge number of blades, the probability of such misbehavior increases.As a result, there is a greater likelihood of a larger number of dataand control traffic exchanges being initiated from multiple sources andit is critical to insulate the fabric from misbehaviors and/or maliciousattacks.

An isolation switch blade is similar to a conventional switch blade inthat it presents standard F_ports (fabric ports to which N_ports attach)to the host blades, but different in that it connects to the enterprisefabric as N_ports (rather than as E_ports) in the preferred embodiment.The isolation switch blade partitions the enterprise storage areanetwork (SAN) into two separate fabrics such that the blade server isconnected to the “blade fabric” and other servers and devices areconnected to the “enterprise fabric.” FIG. 1 shows a possible deploymentof the isolation switch blade in a blade chassis 102 with a series ofhost blades 104 which illustrates how two distinct logical fabrics, theblade fabric 106 and the enterprise fabric 108, are being constructed.The purpose of the blade fabric 106 is to isolate the enterprise fabric108 and provide controlled access to it from host blades 104.

The isolation switch blade 100 replicates some of the functionality of aFibre Channel fabric bridge. However the isolation switch blade 100 isquite different from, and consequently simpler than, a fabric bridge.

As illustrated in FIG. 2, one may dual-connect each host blade 104 tomultiple isolation switch blades 100A, 100B in order to eliminate asingle point of failure. This dual-connect is conventional in existingSANs and the isolation switch blade allows such a configuration to bemaintained.

Fabric scalability is about ensuring that the Fabric OS can reasonablyhandle the peak load conditions induced by ever-larger fabrics duringperiods of intense demand and activity. Such peak loads generallyinvolve fabric-wide events that affect many of the Fabric OS components.Fabric reconfiguration takes place with the introduction and removal ofswitches into the fabric. The reconfiguration process involvescomputation-intensive activities such as rebuilding of fabrics,re-computation of routes, etc. With the introduction of bladed serversand switches, fabrics are expected to become increasingly more dynamic,resulting in an increase in the rate at which these fabric-wide eventsand fabric reconfigurations occur. Hence, the scalability issues may befurther exacerbated.

When an embedded switch in a blade server chassis joins the fabric, theintroduction of the embedded switch typically requires a domain idassignment, routes to be recomputed, zone merges to be done and so on.Since the key capability provided by blade servers is the ability toscale out and provide modularity, the plugging in and out of blades maybe a norm rather than an exception and these fabric reconfigurations aremore likely to take place more frequently.

When a number of blade servers attempt to FLOGI to an embedded switch'sF_port, a large number of updates to the switch's login database may betriggered. A Fibre Channel Protocol (FCP) daemon in the Fabric OS maystart probing the N_ports and send “update area” messages to the nameserver. A large number of probes and name server updates may betriggered, followed by the name server sending Registered State ChangeNotifications (RSCNs), a switch function that allows notification toregistered nodes if a change occurs in the fabric. Similarly, a bladebeing removed from the chassis may trigger updates to the switch logindatabase and name server database and may cause more RSCNs to be sentout to registered devices. A large amount of such internal fabricactivity results in a large amount of processing burden on switch CPUsand this may result in device-initiated exchanges timing out, resultingin devices not being able to receive proper service.

Aspects of the present invention involve isolating blade servers fromthe enterprise fabric via the isolation switch blade 100. This providesa high level of isolation between the host blades 104 and the enterprisefabric 108. Scalability is enhanced due to isolation provided by theisolation switch blades 100 to enterprise fabrics 108 such that theenterprise fabric 108 is not directly impacted when host blades 104 areswapped in and out of the blade fabric 106 and can hence provide a morecontrolled environment to the enterprise fabric 108.

Connecting as an N_port using the NPV mechanism enables the isolationswitch blade 100 to be connected to non-proprietary enterprise fabrics108 and does not have potential interoperability issues of proprietaryE_port implementations.

Since the isolation switch blade 100 places itself in the control pathof any traffic that originates on the host blades 104 and may beintended for the enterprise fabric 108, the isolation switch blade 100is a viable base for hosting software that can perform port and LogicalUnit Number (LUN) filtering, zoning enforcement, stateful inspection,checking for malformed packets, probing for buffer overflows in the FOScopies in the blade center fabric, and performing overall in-bandintrusion detection. In other words, the isolation switch blade 100 canfulfill a secondary purpose of providing enhanced security at theperimeter of the enterprise fabric 108 by acting in the role of a“firewall” by selectively filtering out frames that match certaincriteria of deviant behavior. FIG. 3 shows one such implementation inschematic form wherein a firewall/intrusion detection system is hostedon isolation switch blade 100C.

With this location, the isolation switch blade 100 may also act as aprotocol gateway, such as iSCSI to FCP and so on.

FIG. 4 depicts a typical deployment architecture with a pair ofisolation switch blades (ISB 1 100A and ISB 2 100B) providing dualconnectivity for four host blades (host blade 1 to host blade 4 104A to104D) to two fabrics (A 108A and B 108B). This configuration can besimilarly extended to any number of host blades, isolation switch bladesor enterprise fabrics. For a 16 port isolation switch blade connected totwo fabrics with dual connectivity, up to 14 host blades may beconnected to the isolation switch blade.

The isolation switch blade 100 may be designed to provide path fail-overcapability. FIG. 5 shows an isolation switch blade configuration withpath fail over. If one path to a fabric 108A or 108B is lost due to alink going down between the isolation switch blade 100A or 100B and thefabric 108A, 108B, the isolation switch blade 100A, 100B mayautomatically switch the outgoing traffic to the other port and fill theappropriate SID on the frames, as long as this port is zoned to thetarget, if it is port zoned, based on which port the frames are sentthrough.

A simplified architecture makes certain assumptions regarding thebehavior of host blade host bus adapters. The assumptions are: a) thehost blades 104 can handle or respond to RSCNs when notified aboutchanges to devices connected to the enterprise fabric 108; and, b) inthe case where servers are connected to the same enterprise fabric 108across multiple isolation switch blades 100, it is assumed that theservers have the ability to handle multi-pathing for load balancing orfail over appropriately. In a more complex architecture the isolationswitch blade can handle these functions if needed.

A detailed example of the transfer of frames using an isolation switchblade is shown in FIG. 6A. The isolation switch blade 100 is connectedto a switch 200, which is representative of the enterprise fabric 108,and to a host blade 104. In the illustrated example, port 1 208 of theisolation switch blade 100 is connected to the host blade 104. The port1 208 is configured in F_port mode. Similarly, port 4 212 of theisolation switch blade 100 is connected to a port 9 214 of switch 200, aswitch in the enterprise fabric 108. The port 4 212 is configured inNPV_port mode, while the port 9 214 is configured in F_port mode. A tapedrive unit 204 is connected to port 5 218 of switch 200. It is presumedthat the switch 200 is domain 1 in fabric 108, and the isolation switchblade 100 is domain 0 in blade fabric 106.

Port 4 212 is connected by a private intraswitch link 224 to port 5 210.Port 5 210 is connected to port 1 208 by a private intraswitch link 225.Port 5 210 is configured in loopback mode. This is done because in thepreferred embodiment public and private translations are only performedon the external receiver portion of a port, so an intervening port isneeded to perform address translation. In alternate embodiments eachport can do the necessary address translations and this intermediateport is not needed. The host blade 104 and the tape unit 204 havephantom addresses on the private links 224 and 225. In the illustratedembodiment, the address 04 is provided to the tape unit 204 and theaddress 02 is provided for the host blade 104. Thus private to publictranslations occur at port 5 210 and public to private translationsoccur at port 1 208 and port 4 212. For more detail on performing thesetranslations, please refer to U.S. Pat. No. 6,401,128 entitled “Systemand Method for Sending and Receiving Frames Between a Public Device anda Private Device,” which is hereby incorporated by reference.

In the illustrated embodiment the tape unit 204 receives private address04 and the host blade 104 receives private address 02. Port 5 210 isassigned an address 010900, while port 4 212 is assigned an address of010500. Thus the host blade 104 will address the tape drive 204 byproviding a destination address of 010904 that is a full public address.This address of 010904 is converted by port 1 208 to a private addressof 04. This private address of 04 in turn is translated by port 5 210 toan address of 0105EF, which is the actual address of the tape unit 204in fabric 108. The source address of the host blade 104 is 000101 and isconverted to 02 by port 1 208 and then to 010902 by port 5 210. For thetape unit 204 to address the host blade 104, a destination address of010902 is used. This address of 010902 is converted by port 4 212 into aprivate address of 02. Packets transmitted from port 5 210 to the port 1208 are then converted from this private address of 02 to the desiredaddress of 000101 for the host blade 104 by port 5 210. Similarly, port4 212 converts the tape unit 204 source address of 0105EF to 04 and port5 210 converts this address to 010904.

If public to private address translation as described above is notavailable, other suitable address translation techniques which allowfull wire speed operation may be used.

FIG. 6B illustrates a block diagram of an isolation switch blade 100according to the preferred embodiment. In switch 100 a processor unit402 that includes a high performance CPU, preferably a PowerPC, andvarious other peripheral devices including an Ethernet module, ispresent. Receiver/driver circuitry 440 for a serial port is connected tothe processor unit 402, as is a PHY 406 used for an Ethernet connection.A flash memory 410 is connected to the processor 402 to providepermanent memory for the operating system and other routines of theinterfabric switch 120, with DRAM 408 also connected to the processor402 to provide the main memory utilized in the isolation switch blade100. A PCI bus 412 is provided by the processor 402 and to it isconnected a Fabric Channel miniswitch 414. The Fibre Channel miniswitch414 is preferably developed as shown in U.S. patent application Ser. No.10/123,996, entitled, “Fibre Channel Zoning By Device Name In Hardware,”by Ding-Long Wu, David C. Banks, and Jieming Zhu, filed on Apr. 17, 2002which is hereby incorporated by reference. This application alsodescribes a hardware filtering mechanism that can be used for filtering,zoning, malformed packet detection, intrusion detection and otheraspects of the isolation switch blade 100C. The miniswitch 414 is thuseffectively a 16 port switch. Fourteen ports of the miniswitch 414 areconnected to a series of serializers 418, which are then connected tomedia unit 420. Twelve of the media units 420 are for connection to hostblades 104 and two media units 420 are for connections to enterprisefabric or fabrics 108. Two of the ports of the miniswitch 414 areconfigured in loopback mode such as in port 5 210 in FIG. 6A. There aretwo loopbacks in this embodiment to match the number of enterprisefabric ports. In the preferred embodiment, if two separate enterprisefabrics 108 are connected to the isolation switch blade 100, for exampleas shown in FIG. 4, an additional loopback port may be needed to providean additional address translation for one of the fabrics should theconnected domains of the enterprise fabrics be the same. This case wouldreduce the number of available host blade connections to eleven.

FIG. 6C is an embodiment of an isolation switch blade 100′ with a largernumber of connections for host blades 104. In this embodiment there aretwo miniswitches 414A and 414B. Miniswitch 414B is preferably an eightport device. In this embodiment two ports of miniswitch 414A areconnected to two ports of miniswitch 414B. Each miniswitch 414A and 414Bhas only one port configured in loopback mode. Each miniswitch 414A,414B is configured to have one enterprise fabric connection, with theremainder available for host blades, so that the embodiment providesconnections for up to 16 host blades 104. In this embodiment preferablythe two interswitch links would be configured as private links tominimize the number of hops from an enterprise fabric to a host blade.Thus, if the host blade and the enterprise fabric were connected to thesame miniswitch, the loopback port for that miniswitch would be used foraddress translation. However, if the enterprise fabric and host bladewere connected to different miniswitches, the ports of the interswitchlink would handle the address translation. In the case described abovewhere the connected domains of the enterprise fabrics are the same, theinterswitch links would handle the additionally needed addresstranslation so no additional loopback ports would be needed.

Proceeding then to FIG. 6D, a general block diagram of the isolationswitch blade 100 hardware and software is shown. Block 300 indicates thehardware as previously described. Block 302 is the basic softwarearchitecture of the virtualizing switch. Generally think of this as theisolation switch blade fabric operating system and all of the particularmodules or drivers that are operating within that embodiment. Modulesoperating on the operating system 302 are Fibre Channel, switch anddiagnostic drivers 304; port modules 306, if appropriate; a driver 308to work with the Fibre Channel miniswitch ASIC; and a system module 310.Other switch modules include a fabric module 312, a configuration module314, a phantom module 316 to handle private-public address translations,an FSPF or Fibre Shortest Path First routing module 320, an AS or aliasserver module 322, an MS or management server module 324, a name servermodule 326 and a security module 328. Additionally, the normal switchmanagement interface 330 is shown including web server, SNMP, telnet andAPI modules.

Three additional modules are present according to the present invention.A firewall/intrusion detection module 334 performs those features asdescribed. A PID mapping table 342 is present and accessible by any ofthe modules as needed. Finally, a virtual node port module 338 performsthe node port virtualization function. This module 338 is included inthe drivers 304 in the preferred embodiment.

The link initialization protocol between a host blade 104 and theisolation switch blade 100 and between the isolation switch blade 100and enterprise fabrics 108 is the same as that of a normal F ort asdescribed in the FC-PH and FC-FS standards. Once link initialization iscomplete, the N_port or virtual N_port and F_port are in the activestate. The link initialization between the host blade 104 and isolationswitch blade 100 and between the isolation switch blade 100 and theF_ports of the enterprise fabrics 108 can happen independently of eachother.

The introduction of the first host blade 104 into the blade chassis 102causes an FLOGI into the isolation switch blade 100. This results in theisolation switch blade 100 performing a FLOGI into the enterprise fabric108 and subsequently performing FDISC requests into the enterprisefabric 108 for each host blade 104 that is in the blade chassis 102 toget virtual port id (PID) assignments for the host blades 104. Thisprocess is described more completely in U.S. patent application Ser. No.10/291,331 incorporated by reference above. Within the blade centerfabric 108, the isolation switch blade 100 receives a domain id (thoughin most cases the isolation switch blade 100 would generally be thesingle and thus principal switch in the blade fabric), after which timethe host blades 104 can login to the blade fabric 106.

After link initialization is complete, the blade server's N_port sendsits first FLOGI to the isolation switch blade's F_port in the bladecenter fabric 106. At some point after the isolation switch blade 100has done an FLOGI into the enterprise fabric 108 and received an N_portid, the isolation switch blade 100 may perform an FDISC on behalf of allcurrently connected host blade N_ports and receive their virtual N_portids in the FDISC LS_ACC. The name server of the enterprise fabric willthus be populated with the virtual N_port ids representative of the hostblade 104 N_ports. A mapping of the NPV pid to the N_port pid ismaintained by the isolation switch blade 100 as described below. Sincethe enterprise fabric 108 may not be ready to respond to the FLOGI fromthe isolation switch blade 100, the isolation switch blade 100 mustretry the FLOGI some number of times until successful or disable theport.

The isolation switch blade 100 has to present a facade of a switch tothe host blades 104 and of a host to the enterprise fabrics 108 and beable to propagate any control traffic/management requests between theblade center fabric 106 and the enterprise fabrics 108. This isdescribed below.

During the initial switch and fabric bring-up phases, a large number ofactivities occur simultaneously. The isolation switch blade 100decouples the fabric bring up of the enterprise fabric 108 from theblade center fabric 106 and, as a result, the blade center fabrics 106and enterprise 108 fabrics may be brought up in any order andindependently of each other. The two bring up scenarios are describedbelow.

1. Bringing up the enterprise fabrics before the blade center fabric:

Referring now to FIG. 7, consider enterprise fabrics A and B 108A and108B being brought up first such that these fabrics are built, zoningstarts doing zone merges, and edge devices connected to these fabricstry to do FLOGI and then query the name server (NS). When an isolationswitch blade 100 is connected to fabrics A and B 108A and 108B, it cannow FLOGI into these fabrics. However, if the switches in fabrics A andB 108A and 108B have not completed fabric initialization at this time,the isolation switch blade 100 is connected to them (i.e. not yetobtained their domain IDs), they may disable the port on which theyreceive the FLOGI. Once the domain id has been assigned, they mayre-enable the port. As a result, the enterprise fabrics 108 have anopportunity to quiesce before they respond to the isolation switch blade100 FLOGIs, since the isolation switch blade 100 is attempting toconnect as a device and not as a switch. Eventually, the switch may sendan LS_ACC responding to the FLOGI with an N_port id for the isolationswitch blade 100 port that performed the FLOGI. The isolation switchblade 100 then queries the enterprise fabric 108 name server and usesthe responses to develop a name server for the blade fabric 106.Alternatively, the isolation switch blade 100 may forward the nameserver query from the host blade 104 to the enterprise fabric 108 andreturn the responses back to the host blade 104 after performing thenecessary address translation of the name server response payload.

Subsequently, when a host blade 104, is plugged into the blade chassis102 and a FLOGI is performed from N_port 1 (NP 1) into the isolationswitch blade 100, the isolation switch blade 100 may then send an FDISCto the enterprise fabric 108 for host blade 104 and may receive avirtual N_port id for N_port 1. In an alternate embodiment, the virtualN_port ids can be assigned a priori (i.e. before the host blade 104 isplugged in) to a given slot id so that a virtual PID is assigned beforethe host blade 104 is plugged into the slot. This may provide furtherindependence between the blade fabric 106 and enterprise fabric 108operations. However, this approach may result in unnecessary NS entriesbeing created in the enterprise fabric 108 if the host blades 104 do notexist. Also, Port Logins (PLOGI's) to these virtual N_ports may have tobe rejected in cases where the host blade 104 does not exist or theisolation switch blade 100 may have to handle these exchanges.

The host blade 104 N_port 1 may then register with the name server onthe isolation switch blade 100. Once name server entries from enterpriseFabrics A and B 108A and 108B are imported into the isolation switchblade-100, N_port 1 can do a PLOGI into devices and continue with otheroperations as usual.

2. Bringing up the blade fabric before the enterprise fabrics:

If the isolation switch blade 100 is brought up first, it may be theprincipal switch and assign itself a domain id. When the host blade 104is plugged into the blade server before fabrics A and B 108A and 108Bare brought up, N_port 1 may FLOGI into F_port 1 (FP1) of the isolationswitch blade 100 and register with the name server on the isolationswitch blade 100. However, name server entries from enterprise fabrics108A and 108B may not yet be available to perform FC operations totargets within the enterprise fabrics 108A and 108B. Subsequently,Fabrics A and B 108A and 108B may be brought up and the isolation switchblade 100 may perform FLOGI and FDISC to get a virtual addressassignment for N_port 1 and export name server entries to the isolationswitch blade 100, after which N_port 1 can PLOGI into devices andperform other operations as usual. Other host blades like host blade 104can FLOGI into the isolation switch blade 104 while Fabrics A and B 108Aand 108B are coming up.

Since the blade fabric 106 and enterprise fabric 108 are brought upindependently of each other, service parameters assigned to N_portsduring the fabric login process may be different. The service parametersof importance are the time out values. It is important that theisolation switch blade 100 provide the host blades 104 in the bladefabric 106 with timeout values (E_D_TOV and RA_TOV) that are equal to orless than the timeout values provided by the enterprise fabrics 108 tothe virtual N_ports of the isolation switch blade 100. It is possible toenforce this if the enterprise fabrics 108 are brought up before theblade fabric 106 is brought up. However, in the case that the bladefabric 106 is brought up first, and the timeout values assigned to thehost blade 104 ports happen to be higher than those assigned to thevirtual N_ports by the enterprise fabric 108, the host blades 104 shouldbe forced to log out and log into the isolation switch blade 100 again.

After receiving a LS_ACC for its FLOGI request, each host blade 104 canregister for RSCN, perform a N_port login with the name server of theisolation switch blade 100 and register with the isolation switchblade's 100 name server. FCP probing may also be triggered following theFLOGI and the isolation switch blade's 100 name server may be updated.The host blades 104 may also want to query the name server database andperform N_port login with target devices in the enterprise fabric 108.In order to do this, proxy addresses for the union of name serverentries within the enterprise fabrics 108 need to be assigned and theproxy addresses exposed to the host blades 104. As mentioned earlier, amapping table may be maintained by the isolation switch blade 100. Inaddition to the mappings between the virtual N_port and physical N_portidentifiers, mappings between the proxy addresses and enterpriseaddresses 108 may be maintained in the mapping table.

If the host blades 104 complete their login and registration and theisolation switch blade 100 has not yet completed the linkinitialization, login and FDISC to the enterprise fabrics 108, the hostblades 104 may not yet be able to see the targets connected toenterprise fabrics 100 in the isolation switch blade's 100 name server.The host blade 104 may be able to subsequently PLOGI only when thetargets become visible. This enables the enterprise fabric 108 build tobe completed (all domains are reachable) and routes to be establishedbefore the host blades 104 start querying about or attempt to PLOGI intothe devices connected to the enterprise fabric 108.

On the other hand, if the isolation switch blade 100 has alreadycompleted FLOGI and FDISC with the blade fabrics 106 and enterprisefabric 108 devices have been registered with the NS, the host blades 104can discover devices by querying the isolation switch blade's 100 NS forthe targets. This isolation between the target devices within theenterprise fabrics 108 and host blades 104 enables the enterprisefabrics 108 to be insulated from a large amount of simultaneousactivity.

The addition of an additional host blade 104 into the blade chassis 102may trigger a new FDISC to the enterprise fabric 108 and the assignmentof a virtual N_port id and not a FLOGI. Since FDISC does not trigger FCPprobing and NS updates, this process may be less disruptive to theenterprise fabric 108. The isolation switch blade 100 may handle FCPprobing of the host blades 104 and perform NS updates to its NS databasebased on the probes.

In FIG. 8, PNP1-A is the virtual PID assigned for N_port 1 by Fabric A108A and PNP 1-B is the virtual PID assigned by Fabric B 108B for N_port1. Since PNP 1-A and PNP 1-B are assigned by two independent fabrics,they could be identical and the mapping should be able to handle this.Similarly, the PIDs of devices in Fabric A and B 108A and 108B maycollide and proxy addresses may have to be maintained to provide aunique address space that is scoped by fabric.

In order to create separate namespaces for PIDs per enterprise fabric108 that are connected to the isolation switch blade 100, eachenterprise fabric 108 is assigned a unique identifier by the isolationswitch blade 100, known as the “proxy domain identifier.” The proxydomain identifier may be filled into the “domain” field of the SID/DIDfor frames that are initiated from/targeted to switches/devices in theenterprise fabrics 108A and 108B and the remaining 16 bits of theaddress may be used to uniquely identify ports in each of the fabrics108A and 108B.

Similarly, the virtual PIDs, assigned via NPV, may be used to addressthe isolation switch blade 100 and host blades 104 within the bladefabric 106. The isolation switch blade 100 may map these proxy andvirtual addresses to physical addresses as described below.

Since the isolation switch blade 100 serves as a proxy between the bladeserver and enterprise fabrics 108, it has to map between virtual N_portids assigned by the enterprise fabric 108 and N_port ids assigned by theblade fabric 106. Similarly, it has to map between the virtual proxyaddresses for devices in the enterprise fabric 108 and physicaladdresses. These mappings may be maintained in a separate PID mappingtable.

The PID mapping table contains mappings between physical and virtualhost blade N_port ids and also between physical and proxy enterprisefabric 108 device N_port ids. When control or data frames from the hostblade 104 are targeted to a device in the enterprise fabric 108, the SIDmay be mapped to the virtual N_port id at the isolation switch blade100. The DID may be mapped from the proxy address to the physicaladdress and sent to the right isolation switch blade 100 egress port.These mappings are performed using a PID mapping table. An exemplary PIDmapping table is shown in FIG. 8. This table is used to populate thepublic to private and private to public address translation tables inthe isolation switch blade 100 ports.

The table may be divided into sections that are indexed by the proxydomain identifier and the address of the isolation switch blade 100virtual N_port connected to the enterprise fabrics 108. The Proxy Domaincolumn uniquely identifies the enterprise fabric 108 to which framesfrom the blade fabric 106 get routed. The domain portion of the DID ofall frames targeted to devices in the enterprise fabrics 108 may carrythe proxy domain id. The PID mapping table partitions the PID namespaceso that there is no possibility of PID conflicts. PID1, PID2 etc. arethe physical addresses of ports in the enterprise fabric 108 and PID1′,PID2′ etc. are the corresponding proxy addresses assigned by theisolation switch blade 100.

The isolation switch blade 100 queries the NS of both Fabric A and B108A and 108B and populates the physical addresses and the isolationswitch blade 100 assigns unique logical proxy addresses pre-fixed with aproxy domain id. The isolation switch blade 100 “listens” for devicedetected RSCNs from these fabrics 108A and 108B and updates its mappingtable. The mapping table also contains mappings between all the physicaladdresses (N_port 1, N_port 2 etc.) to virtual N_port id (PNP 1-A,PNP2-A etc.) for N_ports of the host blades 104.

For frames destined to enterprise fabrics 108, the Proxy Domain (PD0,PD1) field in the DID is used to perform the mapping table lookup. Forframes destined from enterprise fabrics 108 to host blades 104, thelookup is performed based on isolation switch blade 100 virtual N_port(NPV1, NPV2).

Host blade 104 may send a frame to a virtual target PID in Fabric A 108Afrom N_port 1. isolation switch blade 100 may check to see if thevirtual PID is within the table partition associated with PD0 or PD1 andtranslate the proxy address to a physical address. Similarly, framesfrom the enterprise fabric 108A to the host blade 104 may be scoped bythe virtual N_port (NPV1 or NPV2) and the virtual N_port ids mapped to aphysical N_port id from the table.

The blade server N_port (N_port 1) initiates a PLOGI to a target usingthe blade fabric 106 N_port id as the SID and the isolation switch blade100 maps the SID to the virtual N_port Id of the enterprise fabric 108.Responses are directed to the virtual N_ports as DIDs and the DIDs aremapped to the blade fabric 106 N_port ids using the mappings in the PIDmapping table. Similarly, the PIDs contained in the data traffic mayrequire a wire-speed mapping of PIDs. Mapping control traffic from thehost blades 104 and the enterprise fabric 108 (such as FLOGIs or PLOGIsto the NS) and traffic from the enterprise fabric 108 to the host blades104 is mediated by the isolation switch blade 100 processor, and themapping is implemented using a logical PID mapping table. The SID/DIDused in management frames for the host blade 104 N_port may be thevirtual PIDs. Some control traffic, such as certain types of ELS and NSresponses, carry PIDs in their payload. In these cases the addresses inthe payloads must also be mapped using the PID mapping table.

The PID mapping table entry may be updated when a PID is assigned by theblade fabric 106 to a host blade 104 N_port and updated whenever acorresponding virtual N_port id is returned by the enterprise fabric 108in response to an FDISC (in the case of pre-provisioned virtual PIDsdescribed earlier, a new entry may be created with the creation of a newvirtual PID). Removal of a host blade 104 may cause removal of thecorresponding virtual N_port id from NS and removal of the PID mappingtable entry.

Only those devices in the enterprise fabric 108 that are zoned to one ormore of the host blade 104 ports in the blade fabric 106 may have anentry in the blade fabric's NS and the PID mapping table. Hence thenumber of entries in the isolation switch blade's 100 PID mapping tablemay be equal to the sum of the total number of devices in the enterprisefabrics 108 that are zoned to one or more of the host blade 104 ports inthe blade fabric 106 and the total number of host blades 104.

As an example, consider a frame initiated from physical address N_port 1of the host blade 104, to target physical address PID1 in enterprisefabric A 108A. The SID/DID fields in the frame headers are:

At host blade 104: SID=N_port 1, DID=PID1′

At isolation switch blade 100: SID=PNP1-A, DID=PID1 (based on lookupindexed by proxy domain id field of DID, PD0).

In Fabric A 108: SID=PNPI-A, DID=PID1

Now consider a frame targeted to physical address N_port 1 of host blade104 from physical address PID1 of initiator in enterprise fabric A 108A.The SID/DID fields in the frame headers are:

In Fabric A 108A: SID=PID1, DID=PNP 1-A

At isolation switch blade 100: SID=PID1′, DID=N_port 1 (based on lookupindexed by isolation switch blade ingress virtual N_port, NPV1).

At host blade 104: SID=PID1′, DID=N_port 1

Following the login and initialization process described above, theenterprise fabric's 108 name server may retrieve new and deleted NPVdevice bitmaps from the switch driver of the switch that was involved inthe NPV. Since device entries for all devices in enterprise fabrics 108are maintained in the PID mapping table, response to all host blade 104requests may be performed by the isolation switch blade 100 and do notneed to trigger queries to the NS on the enterprise fabric 108. Theisolation switch blade 100 may update its own NS based on theregistration and deregistration of host blades 104 and respond to anyhost blade 104 related NS queries. It may register for RSCNs in order toupdate its mapping table when devices enter and leave the enterprisefabric 108. When host blades 104 are pulled out, the NPV ports will sendcorresponding FLOGOs to the enterprise fabric 108 and the isolationswitch blade 100 will flush the addresses of the removed host blades 104from its name server and from its PID mapping table. Such registrationand discovery is illustrated schematically in FIG. 9.

The isolation switch blade 100 does not impact Worldwide Named (WWN)based zoning. For domain, port based zoning, virtual N_port ids may bemapped to PIDs using the PID mapping table. To add a host blade 104N_port to a zone, the virtual PID may be looked up in the PID mappingtable and used as the PID for this port to be zoned. Such zoning isillustrated in FIG. 10 wherein host blades 104A and 104B connect toFabric A 108 via the isolation switch blade 100.

In order to provide fault tolerance and better link utilization that canreduce the possibility of congestion, isolation switch blade 100configurations may be able to support multiple paths from a host blade104 to a target in the enterprise fabric 108. Depending on thecapabilities of the host blade 104, it is possible to perform loadbalancing and/or fail over.

FIG. 11 shows a dual isolation switch blade 100 configuration. Thisconfiguration allows a host blade 104 to be connected to two fabrics Aand B 108A and 108B, over separate isolation switch blades 100A and100B. If the multipathing firmware in the host blade 104 supports loadbalancing, it is possible for the host blade 104 to send frames toFabric A 108A or Fabric B 108B on both N_port 1 and N_port 2.

If the multipathing software is capable of supporting failover, the hostblade 104 can send frames from N_port 2 if the path from N_port 1 to thetarget is not available for any reason, such as link going down orisolation switch blade 104A failing. The isolation switch blades 100A,100B support fail over in that if isolation switch blade 100A fails, itresults in isolation switch blade 100B taking over and the enterprisefabrics 108 are not subjected to disruption.

In order to support in-band fabric management, for queries via CT passthru from the host bus adapter, management CT frames may be allowedthrough the isolation switch blade 100 into enterprise fabrics 108. Inorder to support dynamic queries to the host bus adapter using FDMI-2,CT frames from enterprise fabric 108 switches may be allowed through thehost bus adapter to the host blades 104. CT frames may be directed tothe isolation switch blade's 100 management server and the isolationswitch blade 100 may have the same level of management capabilities asthe management server on any other switch. As mentioned earlier, theisolation switch blade's 100 CPU is responsible for the address mappingsof these CT frames.

In-band discovery from enterprise fabrics 108 may result in theisolation switch blade 100 being discovered as a node that is connectedto that enterprise fabric 108 and hence may result in a partial view ofthe topology. The discovered N_port ids of the host blades 104 may beused to perform zoning.

In band discovery with the isolation switch blade 100 as a proxy mayresult in discovery of switches and devices in the enterprise fabrics108 as well as the discovery of host blades 104 and may result in acomplete topology discovery.

From an element management perspective, the isolation switch blade 100should be treated as a new type of switch that exposes F_ports andN_ports. In order to enforce frame filtering at the isolation switchblade 100, the isolation switch blade 100 may be configured with accesscontrol policies.

In the NPV implementation described in above references, the SID/DIDvalidation in the miniswitch is turned off since NPV requires a PID tobe assigned by the enterprise fabric 108. Hence the DID field in thetransmitted frames and the SID fields in the received frames that areexpected to match at the enterprise fabric's F_port, do not match in thecase of NPV. This opens up security threats since the main purpose ofthe SID/DID checking is to prevent spoofing of authorized devices byunauthorized devices by using the PID of the authorized device. However,since the isolation switch blade 100 is acting as an intermediary inthis case, it can prevent rogue devices from spoofing since the SID/DIDchecking happens at the F_port of the isolation switch blade 100.Further, the security threats can be mitigated using zones of trust.

The FCAP protocol, as explained in U.S. patent application Ser. No.10/062,125 filed Jan. 31, 2002 entitled “Network Security andApplications to the Fabric Environment” which is hereby incorporated byreference, is used by Secure FabOS to establish zones of trust. Hostblades 104 and the isolation switch blade 100 are part of the bladefabric 106 and may be part of that fabric's zone of trust. Similarly,the isolation switch blade 100 may be part of the enterprise fabric's108 zone of trust. FIG. 12 is a schematic representation showing FCAPbetween host blade 104 and the isolation switch blade 100 and betweenthe isolation switch blade 100 and Fabric A 108.

Secure FabOS also has the notion of security policies that limit accessto the fabric. One set of policies, the Device Connection Control (DCC)policies, may be used to determine which host blades 104 are allowed toconnect to F_ports within the enterprise fabric 108. DCC policies may beexported from the enterprise fabrics 108 to the isolation switch blade100 and enforced at the isolation switch blade 100.

Due to the unique placement of the isolation switch blade 100 at theedge of the enterprise fabric 108, it can further bolster thecapabilities of Secure FabOS. Rules can be defined and enforced at theisolation switch blade 100 such that certain frames are filtered out andnot allowed access into the enterprise fabric 108. These rules mighttake the form of access control policies or the form of policies thatdetect patterns in an attempt to differentiate legitimate traffic fromintrusions.

As shown schematically in FIG. 13, another possible implementation of anisolation switch blade 100A, 100B, is to connect to the enterprisefabric 108 as an E_port. The advantage that this provides over the NPVisolation switch blade 100 is the ability to trunk E_ports. However,this configuration needs to virtualize the Fabric OS and run multiplecopies as described in U.S. patent application Ser. No. 10/209,743.Connecting as an E_port also has the disadvantage of possible lack ofinteroperiability due to the general proprietary nature of E-ports.Because of these complexities, the potential advantages provided bytrunking are generally outweighed and the preferred embodiment is asdescribed above, though N_port trunking could provide the benefitswithout the disadvantages.

While the present invention has been described with respect to a limitednumber of embodiments, those skilled in the art will appreciate numerousmodifications and variations therefrom. It is intended that the appendedclaims cover all such modifications and variations as fall within thetrue spirit and scope of this present invention.

1. A data switching device for connecting to a series of nodes and to afirst fabric, the device comprising: a plurality of fabric ports forconnecting to the series of nodes and forming a second fabric; at leastone node port for connecting to the first fabric; and a switch coupledto said plurality of fabric ports and said at least one node port forinterconnecting said ports.
 2. The device of claim 1, wherein said atleast one node port operates as a virtual node port, with one virtualnode address for each of said plurality of fabric ports connected tonodes.
 3. The device of claim 1, wherein said switch is further adaptedto act as a firewall.
 4. The device of claim 1, wherein said switch isfurther adapted for intrusion detection.
 5. The device of claim 1,further comprising: at least one intermediate port coupled to saidswitch, wherein said switch routes frames between said plurality offabric ports and said at least one node port through said at least oneintermediate port.
 6. The device of claim 5, wherein the interconnectionbetween said at least one intermediate port and either said plurality offabrics ports or said at least one node port is a privateinterconnection and said at least one intermediate port and said otherport perform public to private and private to public addresstranslations.
 7. The device of claim 5, wherein the number ofintermediate ports equals the number of node ports.
 8. The device ofclaim 1, wherein said switch performs public to private and private topublic address translations between said plurality of fabric ports andsaid at least one node port.
 9. A Fibre channel switch for connecting toa series of nodes and to a first fabric, the switch comprising: aplurality of F_ports for connecting to the series of nodes and forming asecond fabric; at least one N_port for connecting to the first fabric;and a switch circuit coupled to said plurality of F_ports and said atleast one N_port for interconnecting said ports.
 10. The switch of claim9, wherein said at least one N_port operates as a virtual node port,with one virtual node address for each of said plurality of F_portsconnected to nodes.
 11. The switch of claim 9, wherein said switchcircuit is further adapted to act as a firewall.
 12. The switch of claim9, wherein said switch circuit is further adapted for intrusiondetection.
 13. The switch of claim 9, further comprising: at least oneintermediate port coupled to said switch circuit, wherein said switchcircuit routes frames between said plurality of F_ports and said atleast one N_port through said at least one intermediate port.
 14. Theswitch of claim 13, wherein the interconnection between said at leastone intermediate port and either said plurality of F_ports or said atleast one N_port is a private interconnection and said at least oneintermediate port and said other port perform public to private andprivate to public address translations.
 15. The switch of claim 13,wherein the number of intermediate ports equals the number of N_ports.16. The switch of claim 9, wherein said switch circuit performs publicto private and private to public address translations between saidplurality of F_ports and said at least one N_port.
 17. A networkcomprising: a series of nodes; a first fabric; and a data switchingdevice connected to said series of nodes and to said first fabric, saiddevice including: a plurality of fabric ports for connecting to saidseries of nodes and forming a second fabric; at least one node port forconnecting to said first fabric; and a switch coupled to said pluralityof fabric ports and said at least one node port for interconnecting saidports.
 18. The network of claim 17, wherein said at least one node portoperates as a virtual node port, with one virtual node address for eachof said plurality of fabric ports connected to nodes.
 19. The network ofclaim 17, wherein said switch is further adapted to act as a firewall.20. The network of claim 17, wherein said switch is further adapted forintrusion detection.
 21. The network of claim 17, further comprising: atleast one intermediate port coupled to said switch, wherein said switchroutes frames between said plurality of fabric ports and said at leastone node port through said at least one intermediate port.
 22. Thenetwork of claim 21, wherein the interconnection between said at leastone intermediate port and either said plurality of fabrics ports or saidat least one node port is a private interconnection and said at leastone intermediate port and said other port perform public to private andprivate to public address translations.
 23. The network of claim 21,wherein the number of intermediate ports equals the number of nodeports.
 24. The network of claim 17, wherein said switch performs publicto private and private to public address translations between saidplurality of fabric ports and said at least one node port.
 25. Thenetwork of claim 17, wherein said nodes are host computers.
 26. Thenetwork of claim 25, wherein said host computers are blade computers andare located in a blade server chassis.
 27. The network of claim 26,wherein said data switching device is a blade located in said bladeserver chassis.
 28. A network comprising: a series of nodes; a firstfabric; and a Fibre channel switch connected to said series of nodes andto said first fabric, said switch including: a plurality of F_ports forconnecting to said series of nodes and forming a second fabric; at leastone N_port for connecting to said first fabric; and a switch circuitcoupled to said plurality of F_ports and said at least one N ort forinterconnecting said ports.
 29. The network of claim 28, wherein said atleast one N_port operates as a virtual node port, with one virtual nodeaddress for each of said plurality of F_ports connected to nodes. 30.The network of claim 28, wherein said switch circuit is further adaptedto act as a firewall.
 31. The network of claim 28, wherein said switchcircuit is further adapted for intrusion detection.
 32. The network ofclaim 28, further comprising: at least one intermediate port coupled tosaid switch circuit, wherein said switch circuit routes frames betweensaid plurality of F_ports and said at least one N_port through said atleast one intermediate port.
 33. The network of claim 32, wherein theinterconnection between said at least one intermediate port and eithersaid plurality of F_ports or said at least one N_port is a privateinterconnection and said at least one intermediate port and said otherport perform public to private and private to public addresstranslations.
 34. The network of claim 32, wherein the number ofintermediate ports equals the number of N_ports.
 35. The network ofclaim 28, wherein said switch circuit performs public to private andprivate to public address translations between said plurality of F_portsand said at least one N_port.
 36. The network of claim 28, wherein saidnodes are host computers.
 37. The network of claim 36, wherein said hostcomputers are blade computers and are located in a blade server chassis.38. The network of claim 37, wherein said data switching device is ablade located in said blade server chassis.
 39. A network comprising: aseries of nodes, each having two ports; a first fabric; and two dataswitching devices, each connected to one port of each of said series ofnodes and to said first fabric, each said device including: a pluralityof fabric ports for connecting to said one port of said series of nodesand forming an additional fabric; at least one node port for connectingto said first fabric; and a switch coupled to said plurality of fabricports and said at least one node port for interconnecting said ports.40. The network of claim 39, wherein said at least one node portoperates as a virtual node port, with one virtual node address for eachof said plurality of fabric ports connected to nodes.
 41. The network ofclaim 39, wherein said switch is further adapted to act as a firewall.42. The network of claim 39, wherein said switch is further adapted forintrusion detection.
 43. The network of claim 39, further comprising: atleast one intermediate port coupled to said switch, wherein said switchroutes frames between said plurality of fabric ports and said at leastone node port through said at least one intermediate port.
 44. Thenetwork of claim 43, wherein the interconnection between said at leastone intermediate port and either said plurality of fabrics ports or saidat least one node port is a private interconnection and said at leastone intermediate port and said other port perform public to private andprivate to public address translations.
 45. The network of claim 43,wherein the number of intermediate ports equals the number of nodeports.
 46. The network of claim 39, wherein said switch performs publicto private and private to public address translations between saidplurality of fabric ports and said at least one node port.
 47. Thenetwork of claim 39, wherein said nodes are host computers.
 48. Thenetwork of claim 47, wherein said host computers are blade computers andare located in a blade server chassis.
 49. The network of claim 48,wherein each said data switching device is a blade located in said bladeserver chassis.
 50. A network comprising: a series of nodes, each havingtwo ports; a first fabric; and two Fibre channel switches connected toone port of each of said series of nodes and to said first fabric, eachsaid switch including: a plurality of F_ports for connecting to said oneport of said series of nodes and forming an additional fabric; at leastone N_port for connecting to said first fabric; and a switch circuitcoupled to said plurality of F_ports and said at least one N_port forinterconnecting said ports.
 51. The network of claim 50, wherein said atleast one N_port operates as a virtual node port, with one virtual nodeaddress for each of said plurality of F_ports connected to nodes. 52.The network of claim 50, wherein said switch circuit is further adaptedto act as a firewall.
 53. The network of claim 50, wherein said switchcircuit is further adapted for intrusion detection.
 54. The network ofclaim 50, further comprising: at least one intermediate port coupled tosaid switch circuit, wherein said switch circuit routes frames betweensaid plurality of F_ports and said at least one N_port through said atleast one intermediate port.
 55. The network of claim 54, wherein theinterconnection between said at least one intermediate port and eithersaid plurality of F_ports or said at least one N_port is a privateinterconnection and said at least one intermediate port and said otherport perform public to private and private to public addresstranslations.
 56. The network of claim 54, wherein the number ofintermediate ports equals the number of N_ports.
 57. The network ofclaim 50, wherein said switch circuit performs public to private andprivate to public address translations between said plurality of F_portsand said at least one N_port.
 58. The network of claim 50, wherein saidnodes are host computers.
 59. The network of claim 58, wherein said hostcomputers are blade computers and are located in a blade server chassis.60. The network of claim 59, wherein said data switching device is ablade located in said blade server chassis.
 61. A network comprising: aseries of nodes, each having two ports; first and second fabrics; andtwo data switching devices, each connected to one port of each of saidseries of nodes and to said first and second fabrics, each said deviceincluding: a plurality of fabric ports for connecting to said one portof said series of nodes and forming an additional fabric; two nodeports, one for connecting to each of said first and second fabrics; anda switch coupled to said plurality of fabric ports and said two nodeports for interconnecting said ports.
 62. The network of claim 61,wherein each of said node ports operates as a virtual node port, withone virtual node address for each of said plurality of fabric portsconnected to nodes.
 63. The network of claim 61, wherein said switch isfurther adapted to act as a firewall.
 64. The network of claim 61,wherein said switch is further adapted for intrusion detection.
 65. Thenetwork of claim 61, further comprising: two intermediate ports coupledto said switch, wherein said switch routes frames between said pluralityof fabric ports and said two node ports through one of said intermediateports.
 66. The network of claim 65, wherein the interconnection betweeneach of said intermediate ports and either said plurality of fabricsports or said node ports is a private interconnection and saidintermediate ports and said other ports perform public to private andprivate to public address translations.
 67. The network of claim 61,wherein said switch performs public to private and private to publicaddress translations between said plurality of fabric ports and saidnode ports.
 68. The network of claim 61, wherein said nodes are hostcomputers.
 69. The network of claim 68, wherein said host computers areblade computers and are located in a blade server chassis.
 70. Thenetwork of claim 69, wherein each said data switching device is a bladelocated in said blade server chassis.
 71. A network comprising: a seriesof nodes, each having two ports; first and second fabrics; and two Fibrechannel switches connected to one port of each of said series of nodesand to said first and second fabrics, each said switch including: aplurality of F_ports for connecting to said one port of said series ofnodes and forming an additional fabric; two N_ports, one for connectingto each of said first and second fabrics; and a switch circuit coupledto said plurality of F_ports and said two N_ports for interconnectingsaid ports.
 72. The network of claim 71, wherein each of said N_portsoperates as a virtual node port, with one virtual node address for eachof said plurality of F_ports connected to nodes.
 73. The network ofclaim 71, wherein said switch circuit is further adapted to act as afirewall.
 74. The network of claim 71, wherein said switch circuit isfurther adapted for intrusion detection.
 75. The network of claim 71,further comprising: two intermediate ports coupled to said switchcircuit, wherein said switch circuit routes frames between saidplurality of F_ports and said two N_ports through one of said twointermediate ports.
 76. The network of claim 75, wherein theinterconnection between each of said intermediate ports and either saidplurality of F_ports or said N_ports is a private interconnection andsaid intermediate ports and said other ports perform public to privateand private to public address translations.
 77. The network of claim 71,wherein said switch circuit performs public to private and private topublic address translations between said plurality of F_ports and saidN_ports.
 78. The network of claim 71, wherein said nodes are hostcomputers.
 79. The network of claim 78, wherein said host computers areblade computers and are located in a blade server chassis.
 80. Thenetwork of claim 79, wherein said data switching device is a bladelocated in said blade server chassis.
 81. A network comprising: a seriesof nodes, each having two ports; first and second fabrics; and two dataswitching devices, each connected to one port of each of said series ofnodes and to one of said first and second fabrics, each said deviceincluding: a plurality of fabric ports for connecting to said one portof said series of nodes and forming an additional fabric; two node portsfor connecting to one of said first and second fabrics; and a switchcoupled to said plurality of fabric ports and said two node ports forinterconnecting said ports.
 82. The network of claim 81, wherein each ofsaid node ports operates as a virtual node port, with one virtual nodeaddress for each of said plurality of fabric ports connected to nodes.83. The network of claim 81, wherein said switch is further adapted toact as a firewall.
 84. The network of claim 81, wherein said switch isfurther adapted for intrusion detection.
 85. The network of claim 81,further comprising: two intermediate ports coupled to said switch,wherein said switch routes frames between said plurality of fabric portsand said two node ports through one of said intermediate ports.
 86. Thenetwork of claim 85, wherein the interconnection between each of saidintermediate ports and either said plurality of fabrics ports or saidnode ports is a private interconnection and said intermediate ports andsaid other ports perform public to private and private to public addresstranslations.
 87. The network of claim 81, wherein said switch performspublic to private and private to public address translations betweensaid plurality of fabric ports and said node ports.
 88. The network ofclaim 81, wherein said nodes are host computers.
 89. The network ofclaim 88, wherein said host computers are blade computers and arelocated in a blade server chassis.
 90. The network of claim 89, whereineach said data switching device is a blade located in said blade serverchassis.
 91. A network comprising: a series of nodes, each having twoports; first and second fabrics; and two Fibre channel switchesconnected to one port of each of said series of nodes and to one of saidfirst and second fabrics, each said switch including: a plurality ofF_ports for connecting to said one port of said series of nodes andforming an additional fabric; two N_ports for connecting to one of saidfirst and second fabrics; and a switch circuit coupled to said pluralityof F_ports and said two N_ports for interconnecting said ports.
 92. Thenetwork of claim 91, wherein each of said N_ports operates as a virtualnode port, with one virtual node address for each of said plurality ofF_ports connected to nodes.
 93. The network of claim 91, wherein saidswitch circuit is further adapted to act as a firewall.
 94. The networkof claim 91, wherein said switch circuit is further adapted forintrusion detection.
 95. The network of claim 91, further comprising:two intermediate ports coupled to said switch circuit, wherein saidswitch circuit routes frames between said plurality of F_ports and saidtwo N_ports through one of said two intermediate ports.
 96. The networkof claim 95, wherein the interconnection between each of saidintermediate ports and either said plurality of F_ports or said N_portsis a private interconnection and said intermediate ports and said otherports perform public to private and private to public addresstranslations.
 97. The network of claim 91, wherein said switch circuitperforms public to private and private to public address translationsbetween said plurality of F_ports and said N_ports.
 98. The network ofclaim 91, wherein said nodes are host computers.
 99. The network ofclaim 98, wherein said host computers are blade computers and arelocated in a blade server chassis.
 100. The network of claim 99, whereinsaid data switching device is a blade located in said blade serverchassis.
 101. A method for routing between a series of nodes and a firstfabric using a data switching device, the method comprising: providing aplurality of fabric ports on the device for connecting to the series ofnodes and forming a second fabric; providing at least one node port onthe device for connecting to the first fabric; and interconnecting saidplurality of fabric ports and said at least one node port with thedevice.
 102. The method of claim 101, further comprising operating saidat least one node port as a virtual node port, with one virtual nodeaddress for each of said plurality of fabric ports connected to nodes.103. The method of claim 101, further comprising: routing frames betweensaid plurality of fabric ports and said at least one node port throughat least one intermediate port on the device.
 104. The method of claim103, wherein the interconnection between said at least one intermediateport and either said plurality of fabrics ports or said at least onenode port is a private interconnection and said at least oneintermediate port and said other port perform public to private andprivate to public address translations.
 105. The method of claim 103,wherein the number of intermediate ports equals the number of nodeports.
 106. The device of claim 101, further comprising performingpublic to private and private to public address translations betweensaid plurality of fabric ports and said at least one node port.